Chronic wounds, ulcers, hernias, and gastrointestinal (GI) perforations are injuries that give patients pain due to openings to an external and foreign environment. These injuries are currently treated by mechanical means, including sutures and meshes, which may not be completely effective at preventing reoccurrence of the injury.
Polymers, such as polyvinyl alcohol (PVA) and polyethylene (PE) are capable of undergoing a process known as electrospinning that excites the polymer solution by contact with a high voltage source (above 2 kV) and secretion through a nozzle, and deposits fibers with diameters in the range of nanometers to a grounded substrate. Electrospinning is a useful process for deposition of fibers to be used as scaffolding for tissue engineering purposes, as the architecture for the deposited nanofibers induces cell migration and healing in vivo and in situ.
Electrospinning is a versatile method for generating very thin fibers made of polymers, ceramics, metals, carbon, and/or composite materials. A somewhat similar technique called electrospray can be used to produce a micro/nanometric jet that breaks up to give rise to an aerosol of charged droplets. Electrospray has a proven ability to generate monodisperse aerosols with sizes ranging from a few nanometers to hundreds of microns. Electrospinning, by contrast, typically generates a jet in a high-voltage field to produce elongated polymeric fibers. Compared with electrospray, which uses electro-hydrodynamic forces to generate a number of particles in an aerosol or a hydrosol phase, electrospinning is a more demanding technique that requires the use of a solution with appropriate viscosity, surface tension, and conductivity to produce continuous liquid jets.
In conventional electrospinning, a suitable polymer solution, or melt, is subjected to a high-voltage electrical field to create an electrically charged jet that creates a solid fiber that has removed most of the solvent from the solution, but has not completely removed the solvent and created a ‘dry’ fiber. For example, one electrode from a high-voltage source may be placed into a polymer solution and the other attached to a conductive collector, such as a panel of aluminum foil or a silicon wafer. A typical apparatus for electrospinning utilizes a spinneret with a metallic needle, a syringe pump providing the working fluid to the spinneret, a high-voltage power supply, and a grounded collector. A polymer, sol-gel, or composite solution or melt is loaded into the syringe pump, and this viscous liquid is driven to the needle tip, forming a droplet at the tip. When a voltage is applied to the metallic needle, the droplet is first stretched into a structure called a Taylor cone and, finally, into an electrified jet. The jet is then elongated and whipped continuously by electrostatic repulsion until it is deposited on the grounded collector. The elongation by bending instability results in the formation of uniform fibers that may typically have nanometer-scale diameters.
Also disclosed herein is an electrospinning process for the production of various-sized nanofibers.